A DC power distribution system is defined by, for instance, the EMerge standard. Currently, in a DC power distribution system in accordance with the EMerge standard power bars are always powered at a nominal voltage, even if there is only a very small fraction of load compared to nominal load conditions. Thus, even if electrical devices connected to the power bars are able to manage a standby mode, in which only very little power is consumed by the electrical devices, a power supply device of the DC power distribution system supplies the nominal voltage such that the power supply device is operated in an unfavorable point of operation, at which the efficiency of power supply is very low, for example, below ten percent.